A groundbreaking research project conducted by the University of Southampton has clarified that corals consume microscopic algae residing in their cells, thereby utilizing a nutrient source once assumed to be inaccessible. This revelation solves an enigmatic scientific question commonly referred to as Darwin’s Paradox of Coral Reefs, which ponders how corals are able to thrive in waters low in nutrients.
A recent investigation spearheaded by the University of Southampton in the United Kingdom has elucidated why coral reefs prosper in oceanic regions that ostensibly lack sufficient nutrients. This has been a subject of scientific intrigue ever since the time of Charles Darwin.
The investigation establishes that corals nurture and derive nutrition from their photosynthetic symbionts—microscopic algae that inhabit their cells. This plant-based dietary regimen enables corals to avail themselves of a sizable reservoir of nutrients, previously deemed inaccessible. Essentially, corals consume some of their symbiotic algae to secure the nutrients necessary for their survival.
Professor Jörg Wiedenmann, who heads the Coral Reef Laboratory at the University of Southampton and led this study, remarked, “The question concerning why coral reefs prosper in nutrient-depleted segments of the ocean, known as Darwin’s Paradox of Coral Reefs, has stimulated the discovery of various crucial processes that contribute to explaining this phenomenon. The missing piece of this complex puzzle can now be inserted, resolving this long-standing enigma.”
Coral reefs serve as a habitat and foraging territory for a myriad of organisms. Wiedenmann and his colleagues note that when Charles Darwin voyaged on the HMS Beagle, his initial expertise was in geology. However, as he traversed tropical waters, he grew increasingly engrossed in understanding the formation and geographical distribution of coral reefs. Darwin accurately theorized the geological interactions responsible for the development of extensive reef structures, but the biological processes facilitating this rapid growth remained unexplored until now.
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Cooperative Survival
Stony corals, though they may appear plant-like, are actually soft-bodied animals. They comprise numerous individual polyps that cohabit in colonies, secreting limestone skeletons to construct what is commonly referred to as ‘reefs’. These reefs are not only vital marine ecosystems but also support about 25% of worldwide oceanic biodiversity and furnish sustenance and income to approximately 500 million individuals globally.
The relationship between coral animals and their microscopic, photosynthetic algae symbionts is symbiotic in nature. The algae generate large quantities of carbon-rich compounds like sugars, which are then transferred to the corals for energy. Furthermore, these algae are adept at absorbing dissolved inorganic nutrients like nitrate and phosphate from seawater.
Scientific Discoveries
Contrary to their algae companions, the corals themselves cannot directly utilize dissolved inorganic nutrients. It was previously ambiguous how these nutrients could promote coral growth. However, scientists from the University of Southampton collaborated with experts from Lancaster University in the UK, Tel Aviv University, and the University of Jerusalem in Israel to identify the mechanism responsible for the transfer of these essential growth nutrients.
Published in the esteemed journal Nature, the researchers revealed that through extended experiments at the University of Southampton’s Coral Reef Laboratory, corals were found to ingest some of their symbionts to acquire the essential nutrients of nitrogen and phosphorus. Empirical data from coral reef atolls in the Indian Ocean corroborated these laboratory results, indicating that this mechanism significantly enhances coral growth at an ecosystemic level.
Dr. Cecilia D’Angelo, an Associate Professor of Coral Biology at Southampton, elaborated, “Over the years, we observed that the symbiotic corals in our experimental setups thrived even without supplemental feeding. The current understanding did not account for how nutrients could be exchanged between the symbiotic partners, which led us to believe that a vital aspect of this relationship was yet to be understood.”
Implications for Climate Change
While excess nutrient enrichment due to human activities can be detrimental to coral reefs, global warming may exacerbate this by disrupting natural nutrient flows. The team’s findings suggest that while coral organisms may withstand brief spells of nutrient deprivation by feeding on their symbionts, sustained nutrient scarcity induced by climate change may pose substantial risks to some coral reefs.
Reference: “Reef-building corals farm and feed on their photosynthetic symbionts” by Jörg Wiedenmann, Cecilia D’Angelo, M. Loreto Mardones, Shona Moore, Cassandra E. Benkwitt, Nicholas A. J. Graham, Bastian Hambach, Paul A. Wilson, James Vanstone, Gal Eyal, Or Ben-Zvi, Yossi Loya and Amatzia Genin, published on 23 August 2023, in the journal Nature.
DOI: 10.1038/s41586-023-06442-5
Frequently Asked Questions (FAQs) about Darwin’s Paradox of Coral Reefs
What is Darwin’s Paradox of Coral Reefs?
Darwin’s Paradox refers to the long-standing question of how coral reefs are able to thrive in nutrient-poor oceanic waters. The phenomenon has intrigued scientists since Charles Darwin’s time.
Who conducted the study that solved Darwin’s Paradox?
The study was led by the University of Southampton in the United Kingdom. The research team collaborated with scientists from Lancaster University in the UK, Tel Aviv University, and the University of Jerusalem in Israel.
How do corals get the nutrients they need to survive?
The study discovered that corals feed on microscopic algae, known as symbionts, that live inside their cells. These algae produce essential nutrients, allowing corals to thrive even in nutrient-poor waters.
What are the implications of this discovery for coral reef ecosystems?
Understanding how corals source nutrients is crucial for conservation efforts, especially given the stresses of global warming. This discovery provides insight into the biological mechanisms that allow coral reefs to flourish in varying conditions.
What methods were used in the study?
The researchers conducted long-term experiments at the University of Southampton’s Coral Reef Laboratory. They used isotopic labeling to trace nutrient flow between the coral host and the symbiotic algae.
How is this study relevant to the impact of global warming on coral reefs?
The findings suggest that while coral reefs may endure brief periods of starvation by feeding off their symbionts, some may be at risk in the face of prolonged nutrient depletion due to global warming.
Where were the study’s findings published?
The findings were published in the scientific journal Nature, under the title “Reef-building corals farm and feed on their photosynthetic symbionts.”
Who is Professor Jörg Wiedenmann?
Professor Jörg Wiedenmann is the Head of the Coral Reef Laboratory at the University of Southampton and led the study that solved Darwin’s Paradox of Coral Reefs.
What role do symbiotic algae play in coral nutrition?
The symbiotic algae are photosynthetic organisms that produce carbon-rich compounds such as sugars. They also efficiently absorb dissolved inorganic nutrients from seawater, which are then made available to the coral host.
What are some of the practical applications of this research?
This research can inform conservation strategies aimed at safeguarding coral reef ecosystems, particularly in the context of environmental stresses such as global warming and nutrient enrichment.
More about Darwin’s Paradox of Coral Reefs
- University of Southampton’s Coral Reef Laboratory
- Nature Journal Publication
- Darwin’s Paradox: An Introduction
- Impacts of Global Warming on Coral Reefs
- Coral Reef Conservation
- Lancaster University Marine Ecology Research
- Tel Aviv University Coral Reef Studies
- University of Jerusalem Marine Biology
- Symbiosis in Coral Reefs
- Impact of Nutrient Enrichment on Coral Reefs
